Freshwater is in demand throughout the world. Freshwater is required for domestic, agricultural, and industrial applications. The highest grade of freshwater, called potable water, is used for human consumption, whereas other grades of freshwater, called brackish water, are used for agricultural and industrial applications. Due to population increases, global warming and other factors, potable water is not available in many areas. The lack of potable water has led to disease and death. Similarly, shortages in various grades of brackish water for agricultural and industrial applications also inhibits the advancement of countries. Accordingly, new systems and methods for producing freshwater are needed in the world.
Although about 70% of the earth is covered by water, most of it is in the form of seawater. Currently there are two major desalination methods for producing freshwater from seawater: distillation and reverse osmosis. Distillation uses evaporation to separate dissolved solid contaminants from seawater to produce freshwater. One shortcoming of distillation is that it requires large amounts of energy and equipment, and produces large amounts of brine containing the contaminants.
Reverse osmosis uses polymer membranes to separate contaminants, particularly dissolved ions, from the seawater. In addition, reverse osmosis (RO) uses pressure to drive the water molecules of seawater through the membrane. In a membrane system, the seawater on the high pressure side of the membrane is called the feed stream, the liquid that has passed through the membrane to form the freshwater is called the permeate, and the liquid containing the solid contaminants is called the concentrate. Reverse osmosis (RO) requires energy to produce fresh water at a pressure differential, which is about 500-900 psi (35-63 kg/cm2). Conventional land based reverse osmosis (RO) is also not efficient, as multiple pumping stages are required. Additionally, the concentrate has a high TDS (total dissolved solids) and can be difficult to dispose of without adverse environmental affects.
The present disclosure is directed to a desalination system and method for producing freshwater that uses high ocean water pressure and a pumped low pressure water to create a pressure differential to drive a reverse osmosis (RO) process of seawater. Less energy is therefore required as only one pressure gradient stage is required while using nature for the high pressure side. In addition, the concentrate produced by this reverse osmosis (RO) is absorbed back into the ocean, such that disposal of the concentrate can be accomplished by natural circulation.
However, the foregoing examples of the related art and limitations related therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings.